define e value

Let's look at a few examples (1) struct{int x; int y;} Test1; Well, define the structure test1, test1.x and test1.y can be used in the statement. (2) struct test {int x; int y;} Test1; Well, define the structure test1, test1.x and test1.y can be

The use of a typedef In C/s + + language, a typedef is commonly used to define an identifier and a keyword alias, which is part of the language compilation process, but it does not actually allocate memory space, as in the case of: typedef int INT;

Usage and difference between typedef and # define I. Usage of typedef In C/C ++, typedef is often used to define an alias for an identifier and a keyword. It is part of the language compilation process, but it does not actually allocate memory

1 NO parameter macro definitionThe macro name of the parameterless macro is not followed by a parameter.The general form of its definition is:#define Identifier stringWhere the "#" indicates that this is a preprocessing command. All that begin with "

Usage of "#" and "#" in macroI. general usageWe use # to convert the macro parameter into a string, and # to combine the two macro parameters.Usage:# Include# IncludeUsing namespace STD; # Define STR (s) # s# Define cons (a, B) int (A ## e ## B) Int

Transferred from: http://www.cnblogs.com/kerwinshaw/archive/2009/02/02/1382428.htmlI. Usage of typedefA typedef is commonly used to define an identifier and an alias for a keyword in the C + + language, which is part of the language compilation

Usage and differentiation of typedef and # defineI. Usage of typedefA typedef is commonly used to define an identifier and an alias for a keyword in the C + + language, which is part of the language compilation process, but it does not actually

Section 2 Interface Definition   Technically, an interface is a set of data structures that contain functional methods. Through this set of data structures, the customerCodeYou can call the functions of component objects. The interface is

Ifndef _i386_errno_h#define _i386_errno_h#define EPERM 1/* Operation not permitted * *#define ENOENT 2/* No such file or directory */#define ESRCH 3/* No such process * *#define EINTR 4/* Interrupted system call * *#define EIO 5 */I/O error *

# Ifndef # define # endif usage, # Ifndef # define # endif usage   # Ifndef # Ifndef in the header, which is critical. For example, you have two C files, both of which include the same header file. During compilation, these two C files need to be